Long-term forage yield and botanical composition dynamics in an andosol grassland under 54 years of fertilizer treatments

Herein, a long-term fertilizer application trial was conducted on a clover (CL)–grass mixed sown grassland established on the andosols in Hokkaido's Konsen district. The experiment combined the presence or absence of the three main nutrients—nitrogen (N), phosphorus (P) and potassium (K)—with or without calcium (Ca) and magnesium (Mg) fertilization. We assessed the influence of fertilization on forage yield and alterations in botanical composition up to the 54th year following establishment. The treatments that maintained high yield levels for >50 years were the no nitrogen (−N) and three-nutrients (3F) plots with Ca and Mg applications. These findings support the statement by Omura et al. (1985) that stable high-yield forage production requires maintaining sown species in the Konsen region, especially CL, restraining N fertilization, applying sufficient P and K, and maintaining an appropriate soil pH through Ca and Mg fertilization. Contrastingly, the continuation of the trial clearly showed its high adaptability to low soil pH, although the redtop (RT, Agrostis alba L.) had previously been regarded only as tolerant to low-P conditions.